Principles Flashcards
(220 cards)
1
Q
What is a cell?
A
Basic structural unit of all living organisms
2
Q
What is a eukaryotic cell?
A
Cell with a true nucleus
3
Q
What is the function of the plasmalemma (cell membrane)?
A
Separates the cytoplasm from the outside environment
4
Q
What is the composition of the plasmalemma?
A
Amphipathic phospholipid bilayer
Integral proteins
Peripheral proteins
5
Q
What roles to membrane proteins play within the cell?
A
Receptors CHannels Transporters Enzymes Cell attachment proteins
6
Q
What do exocytosis and endocytosis mean?
A
Removal of molecules from cell via the cell the plasmalemma
the entry of molecules to the cell via the plasmalemma
7
Q
What are the characteristics of the cell membrane?
A
Fluid
proteins can diffuse laterally or are anchored- not evenly distributed
Selectively permeable- impermiable to charged ions
8
Q
What is an organelle?
A
Small intracellular organs with specific function and structural organization. Essential to life.
9
Q
Give examples of cell organelles.
A
Mitochondria Rough ER Smooth ER Golgi apparatis Lysosomes Nucleus
10
Q
What is a inclusion?
A
Dispensible and transciet. Represent components that have been synthesised by the cell or taken up from extracellular environment
11
Q
What is the function of the cytoskeleton?
A
Maintain cell shape and integrity and leads to locamotion and contraction by filamentous cytosolic proteins, the cytoskeletal proteins
it is joined to the cell membrane
12
Q
What are the three main cytoskeletal proteins?
A
Microfilaments (thinnest)
Intermediate filaments
Thick filaments: Microtubules
13
Q
What are microfilaments composed of?
A
Actin
14
Q
What are microtubules composed of?
A
Two tubulin proteins (alternating alpha and beta)
Include MAP proteins
15
Q
Where do microtubules originate from?
A
Centrosome
Polymerize in central portion of the cell and radiate out- POLAR
16
Q
What is the function of microfilaments?
A
Dynamic- assemble and dissociate
17
Q
What is the function of intermediate filaments?
A
Bind intracellular elements together and to the plasmalemma
Used in identifying tumour origins
18
Q
What is the function of microtubules?
A
Mototway network
Dynein and kinesin attach to microtubules and move along them.
They associate with the membranes of the organelles and vesicles and ‘drag’them along the microtubule.
19
Q
What is kinesin?
A
An ATPase that moves towards the cell periphery
20
Q
What is dynein?
A
An ATPase that moves toward the cell centre
21
Q
What is the function of the nucleus?
A
Contains chromosomes and is the location of mRNA and tRNA synthesis
rRNA is synthesized in the nucleolus
22
Q
What is the structure of the nucleus?
A
Enclosed by a nucleur envelope
Composed of an inner and outer nuclear membrane with nuclear pores.
Between these two sheets is the perinuclear cistern- continous with cistern of the ER
Outer membrane studded with ribosomes- continuous with the rough ER
Nucleolus
23
Q
What is euchromatin?
A
DNA actively undergoing transcription
24
Q
What is heterochromatin?
A
DNA that is condensed and not undergoin transcription
25
What are ribosomes made up of?
Small subunit- binds RNA
| Large subunit- catalyses the formation of peptide bonds
26
What is the role of the rough ER?
Synthesis of proteins
| Metabolically active cells have a lot of ER
27
What are polysomes?
Site of synthesis of proteins that are to remain unpackage and free within the cytosol
28
What is the role of the smooth ER?
The SER continues the processing of proteins produced in the RER.
The SER plays a vital role as the site of the synthesis of lipids.
Most cells contain relatively little SER, but in some (e.g. cells synthesizing steroid hormones) it is extensive.
29
What is the role of the Golgi apparatus?
Transport vesicles arrive at the Golgi from the SER.
Golgi cisterns function in the modification and packaging of macromolecules that were synthesised in the ER.
Adds sugars
Cleaves some proteins
Sorts macromolecules into vesicles.
30
What is the golgi apparatus composed of?
The Golgi apparatus (complex) is composed of a group of flattened, membrane bound cisternae. These are arranged in sub-compartments.
31
What are mitochondria composed of?
They are composed of an outer and an inner membrane. The inner membrane is extensively folded to form cristae, which act to increase the available surface area.
32
What is the function of the mitochondria?
Mitochondria are the power generators of the cell. They function in the generation of ATP, via oxidative phosphorylation, and in the synthesis of certain lipids and proteins.
33
What are lipid droplets?
Lipid droplets are an example of an inclusion and they are not surrounded by a membrane.
34
What are intercellular junctions?
Intercellular junctions are specialized membrane structures which link individual cells together into a functional unit. They are particularly prominent in epithelia
35
What are the three main types of intercellular junctions?
Occluding junctions/tightjunctions/zonula occludens: link cells to form a diffusion barrier- prevent diffusion.
Anchoring junctions/zonula adherens: provide mechanical strength- link actin bundles via cadherin
Communicating junctions: allow movement of molecules between cells.
36
What is a desmosome?
Links submembrane intermediate filaments of adjacent cells- common in skin
37
What are hemidesmosomes?
Link submembrane intermediate filaments of a cell to the extracellular matrix through the transmembrane proteins
38
What is a junctional complex?
Close association of several types of junctions found in certain epithelial tissues
39
What is the role of communicating junctions?
Allow selective diffusion of molecules between adjacent cells.
Often termed gap junctions.
Each junction is a circular patch studded with several hundred pores.
Pores are produced by connexon proteins.
Found in epithelia, but also in some smooth muscle and in cardiac muscle, where it is critical for the spread of excitation.
40
What is endocytosid?
Material from the extracellular space can be incorporated into the cell by endocytosis. The cell membrane invaginates, fuses and the newly made endocytotic vesicle (endosome) buds into the cell. This process is often receptor mediated.
Exocytosis works in reverse to discharge material from the cell
41
What is phagocytosis?
Bacteria or larger particulate material from the extracellular space can be incorporated into the cell by phagocytosis. The bacterium binds to cell surface receptors triggering extensions of the cell to engulf it forming a phagosome. The phagosome binds with a lysosome carrying digestive enzymes producing a phagolysosome.
42
What chemical is used to fix tissues to preserve them as specimens?
Formalin- chemical that cross links proteins
43
What steps are taken to prepare a specimen for light and electon microscopy?
Tissue fixed
Thinly sliced
Impregnated with support material-tissue dehydrated then place in hot wax
Thin sections cut on a microtome and put onto slides
Wax washed out and tissue rehydrated
44
What is the term to describe distortions.changes of the histological tissue when preserved?
Artifacts eg shrinkage
45
What stains are typically used?
Haematoxylin- affinity for acidic molecules and stains them purplish blue eg nucleus
Eosin- affinity for basic molecule and stains them pinish red eg cytoplasm is basic
46
Name the four tissue types.
Epithelium
Connective
Muscle
Nervous
47
What is epithelia?
Cover surfaces of the body or lines hollow organs and also forms glands
48
What is connective tissue?
Connective tissue forms the framework of the body, but beyond that it has a dynamic role in the development, growth and homeostasis of tissues, and, via fat, in energy storage.
49
What is muscle?
Cells that are specialised to generate contraction
50
What is nervous tissue?
Consists of neurons and their supporting cells.
51
What is the function of nervous tissue?
Serves as a control function and allows rapid communication between body parts
52
What characteristics are common to all epithelia?
```
Strong adhesion between cells
Minimum space between cells
Basal lamina
Non vascular
Polarised
```
53
What is a basal lamina?
A layer of extracellular matrix components on the basal surface of an epithelial cell
54
Name an example of epithelial glandular tissue?
Liver tissue
55
What are the functions of epithelia?
Mechanical barrier eg skinChemical barrier (e.g. lining of stomach)
Absorption (e.g. lining of intestine)
Secretion (e.g. salivary gland)
Containment (e.g. lining of urinary bladder)
Locomotion (by cilia) (e.g. oviduct)
Minor functions include: sensation (neuroepithelium, e.g. taste buds) and contractility (myoepithelial cells)
56
What are the three cell shapes of covering epithelia?
Squamous (flattened, like a fish scale)
Cuboidal (cube shape_
Columnar (column, long and thin)
57
What are the terms to describe the number of layers of epithelium?
```
Simple= one layer
Stratified= two or more
Pseudostratified= appears to have multiple layers but is actually only one
```
58
What are goblet cells?
Single mucous glands
59
What is the role of glandular epithelia?
produce secretory products, for example: sweat, milk, oil, hormones, mucous, enzymes
60
What is an endocrine gland?
Ductless
Secrete toward the basal end of the cell
Distribute into the vascular system throughout body
61
What is exocrine glands?
Ducted
| Product secreted towars apical end into either the lumen of an internal space, a duct, or the body surface
62
What are the subdivisions of connective tissue?
Soft- tendons, ligaments, mesentary
Hard- bone and cartilage
Blood and lymph - some consider a connective tissue
63
What does connective tissue consist of?
Extracellular matrix and cells
64
What can the extracellular matrix of connective tissue consist of?
Fibres: collagen, reticular and elastic fibers
Ground substance: an amorphous, space occupying material made of huge unbranched polysaccharide molecules called glycosaminoglycans (GAGs), most of which are bound to protein cores to form glycoproteins
Tissue fluid
65
What do the cells of connective tissue consist of?
Fibroblasts- produce and maintain extracellular matix
Adipose cells- fat cells
Osteocytes- bone cells
Chondrocytes- cartilage
66
What are the types of soft connective tissue?
Loose- fibres separated by abundant ground substances
| Dense- packed full of collagen fibres
67
Name the two types of dense soft connective tissue.
Dense regular CT- fibres aligned eg tendon
| Dense irregular CT - fibres run in many directions eg skin dermis
68
What are the characteristics of cartilage?
Strong, flexible, compressible, semi rigid
| Avascular
69
Where does the semi rigid nature of cartilage come from?
Highly hydrated nature of the ground substance
70
Name the three types of cartilage
Hyaline
Elastic
Fibrocartilage
71
Where is hyaline cartilage found?
Articular surfaces
Tracheal rings
Costal cartilage
Epiphyseal Growth Plates
72
What two types of bone make up the long bones?
Cortical bone- the shaft
Cancellous or trabecular bone- the ends- meshwork
Note bone is living tissue with blood vessels and nerves and osteocytes
73
How does muscle contraction come about?
Force is produced by the movement of actin fibres over myosin fibres, with the aid of a number of accessory proteins.
74
What are the three types of muscle?
Smooth
Skeletal
Cardiac
75
What are the characteristics of smooth muscle?
Involuntary
No striations
Visceral
76
What are the characteristics of skeletal muscle?
Voluntary
| Striated
77
What are the histological aspects of skeletal muscle?
Multinucleated
Cylindrical
Nuclei of of the fibres are elongated and located at the periphery of the cells- SARCOLEMMA
78
Is cardiac muscle striated or non striated?
Striated- less prominant than skeletal msucle
79
What are the histological aspects of cardiac muscle cells?
Single nucleus near centre of the fibre
| Intercalated disc- site of end to end attachment of adjacent cells
80
What does nervous tissue consist of?
Neurons
Glia (support cells)
Surrounded by connective tissue coat- meninges in CNS and epineurium in PNS
81
What are the three types of neurons
Bipolar
Unipolar
Multipolar
82
What are the three types of glia of the CNS?
Astrocytes- support, ion transport
Oliodenrocytes- produce myelin
MIcroglia- immune surveillance
83
What is the principle glia of the PNS?
Schwann cells- produce myelin and support axons
84
What are the three major salivary glands?
Parotid
Submandibular
Sublingual
85
What is the difference between serous and mucous secreting cells?
Serious cells stain intensely- mucous do not
86
How do the salivary gland differ in terms of their histology?
Parotid is serous.
| Submandibular and sublingual are more mucous.
87
What is an unusual feature of salivary glands?
Striated ducts
88
What is a striated duct?
Ducts modify the saliva by pumping salt out of the saliva- becomes hypotonic to the blood- this is why saliva doesnt taste salty!
89
What are the four major layers of the digestive tract?
Mucosa- Submucosa-Muscularis Externa-Serosa or Adventitia
90
What is the digestive mucosa made up of?
Epithelium-Lamina Propria- MUscularis Mucosae
91
What is the submucosa of the digestive tract?
Loose connective tissue
92
What is the muscularis externa made up of?
Inner cricular layer and an outer longitudinal layer
93
What is the function of the serosa or adventitia?
outer layer of connective tissue that either suspends the digestive tract or attaches to other organs
94
What are the characterisitcs of protective mucosa?
Non-keritanised- stratified squamous epithelium
95
Where is protective mucosa found in the GI tract?
Oral, pharynx, oesophagus, anal canal
96
What are the characterisitcs of absorptive mucosa?
Simple- columnar- tubular glands- small intestine
97
What are the characteristics of secretory mucosa?
Simple- columnar-extensive tubular glands-Stomach
98
Where is protective and absorptive mucosa found?
Large intestine
99
WHat are the characteristics of protective and absorptive mucosa?
Simple- columnar- epithelium-tubular glands
100
Explain what teniae coli is.
in the large intestine the outer, longitudinal smooth muscle is not continuous. Instead it is found in 3 muscular strips called teniae coli.
101
What is the name of the GI tracts own nervous system?
Enteric nervous system
101
What is the name of the GI tracts own nervous system?
Enteric nervous system
102
Where are the neurons situated in the enteric nervous system?
Live in groups called ganglia between the two muscle layers that make up the muscularis externa
102
Where are the neurons situated in the enteric nervous system?
Live in groups called ganglia between the two muscle layers that make up the muscularis externa
103
What are the histological layers of the trachea?
Epithelium-Lamina propria- seromucous glad in the submucosa- Hyaline cartilage of the tracheal ring
103
What are the histological layers of the trachea?
Epithelium-Lamina propria- seromucous glad in the submucosa- Hyaline cartilage of the tracheal ring
104
What is the histological difference between the bronchi and the bronchioles?
Bronchi- large diameter and have hyaline cartilage in their wall.
Bronchioles- smaller, no cartilage and smooth muscle predominates in their wall.
104
What is the histological difference between the bronchi and the bronchioles?
Bronchi- large diameter and have hyaline cartilage in their wall.
Bronchioles- smaller, no cartilage and smooth muscle predominates in their wall.
105
What happens to the columnar cells of the epithelium as you move down the respiratory tree?
Get shorter- gas exchange does not occur across these epithelia
105
What happens to the columnar cells of the epithelium as you move down the respiratory tree?
Get shorter- gas exchange does not occur across these epithelia
106
What type of epithelium lines the alveoli?
Simple squamous
106
What type of epithelium lines the alveoli?
Simple squamous
107
What is the name of the GI tracts own nervous system?
Enteric nervous system
107
What is the name of the GI tracts own nervous system?
Enteric nervous system
108
Where are the neurons situated in the enteric nervous system?
Live in groups called ganglia between the two muscle layers that make up the muscularis externa
108
Where are the neurons situated in the enteric nervous system?
Live in groups called ganglia between the two muscle layers that make up the muscularis externa
109
What are the histological layers of the trachea?
Epithelium-Lamina propria- seromucous glad in the submucosa- Hyaline cartilage of the tracheal ring
109
What are the histological layers of the trachea?
Epithelium-Lamina propria- seromucous glad in the submucosa- Hyaline cartilage of the tracheal ring
110
What is the histological difference between the bronchi and the bronchioles?
Bronchi- large diameter and have hyaline cartilage in their wall.
Bronchioles- smaller, no cartilage and smooth muscle predominates in their wall.
110
What is the histological difference between the bronchi and the bronchioles?
Bronchi- large diameter and have hyaline cartilage in their wall.
Bronchioles- smaller, no cartilage and smooth muscle predominates in their wall.
111
What happens to the columnar cells of the epithelium as you move down the respiratory tree?
Get shorter- gas exchange does not occur across these epithelia
111
What happens to the columnar cells of the epithelium as you move down the respiratory tree?
Get shorter- gas exchange does not occur across these epithelia
112
What type of epithelium lines the alveoli?
Simple squamous
112
What type of epithelium lines the alveoli?
Simple squamous
113
What is the name of the GI tracts own nervous system?
Enteric nervous system
114
Where are the neurons situated in the enteric nervous system?
Live in groups called ganglia between the two muscle layers that make up the muscularis externa
115
What are the histological layers of the trachea?
Epithelium-Lamina propria- seromucous glad in the submucosa- Hyaline cartilage of the tracheal ring
116
What is the histological difference between the bronchi and the bronchioles?
Bronchi- large diameter and have hyaline cartilage in their wall.
Bronchioles- smaller, no cartilage and smooth muscle predominates in their wall.
117
What happens to the columnar cells of the epithelium as you move down the respiratory tree?
Get shorter- gas exchange does not occur across these epithelia
118
What type of epithelium lines the alveoli?
Simple squamous
119
What is the name of the GI tracts own nervous system?
Enteric nervous system
120
Where are the neurons situated in the enteric nervous system?
Live in groups called ganglia between the two muscle layers that make up the muscularis externa
121
What are the histological layers of the trachea?
Epithelium-Lamina propria- seromucous glad in the submucosa- Hyaline cartilage of the tracheal ring
122
What is the histological difference between the bronchi and the bronchioles?
Bronchi- large diameter and have hyaline cartilage in their wall.
Bronchioles- smaller, no cartilage and smooth muscle predominates in their wall.
123
What happens to the columnar cells of the epithelium as you move down the respiratory tree?
Get shorter- gas exchange does not occur across these epithelia
124
What type of epithelium lines the alveoli?
Simple squamous
125
What is the name of the GI tracts own nervous system?
Enteric nervous system
126
Where are the neurons situated in the enteric nervous system?
Live in groups called ganglia between the two muscle layers that make up the muscularis externa
127
What are the histological layers of the trachea?
Epithelium-Lamina propria- seromucous glad in the submucosa- Hyaline cartilage of the tracheal ring
128
What is the histological difference between the bronchi and the bronchioles?
Bronchi- large diameter and have hyaline cartilage in their wall.
Bronchioles- smaller, no cartilage and smooth muscle predominates in their wall.
129
What happens to the columnar cells of the epithelium as you move down the respiratory tree?
Get shorter- gas exchange does not occur across these epithelia
142
What type of epithelium lines the alveoli?
Simple squamous
143
What is the arrangement of the lobules in the liver?
Hexagonal
144
What is at each corner of the hexagon in the lobules of the liver?
Hepatic portal vein and hepatic artery
145
What is at the centre of the lobule?
central vein
146
Where does the ventral vein drain to?
The hepatic vein
147
What are liver cells called?
Hepatocytes
148
What makes up the portal triad?
Hepatic portal vein, bile duct, hepatic arteriole.
149
What are the spaces for blood flow in the liver called?
Sinusoids
150
What type of gland is the pancreas?
Exocrine and endocrine
151
What does the exocrine pancreas produce?
Digestive juices containing proteases, lipases and nucleases.
152
How do digestive juices enter the duodenum?
via the pancreatic duct
153
What does the endocrine pancreas consist of?
Islets of langerhans
154
What is produced in the islets of langerhans?
Insulin
155
What is the renal corpuscle?
A tuft of capillaries surrounded by epithelium where the production of urine begins in the kidney
156
What is the kidney composed of ?
Nephrons
157
What are nephrons composed of?
Renal corpuscle/tubule units.
158
What are the constituents of blood?
Plasma (55%) and cells (45%)
159
What is another name for red blood cells?
erthrocytes
160
What is significant histologically about RBCs?
they lack a nucleus
161
What are the five types of WBCs?
Neutrophiles, eosinophiles, basophils, monocytes, lymphocytes
162
What is the collective name for eosinophils, basophils and neutrophils?
Granulocytes
163
What are the three layers of a muscular artery?
Tunica intima (extends to an internal elastiv membrane), tunica media, tunica adventitia
164
What separates the tunica media and the tunica adventitia?
External elastic membrane
165
What is the simple squamous epithelium of blood vessels called?
endothelium
166
What is different about arterioles?
Arterioles have only one or two layers of smooth muscle in their tunica media and almost no adventitia.
167
What are capillaries composed of?
endothelial cells and a basal lamina
168
How is the lymph vascular system unique?
No central pump, but smooth muscle in walls, hydrostatic pressure in the tissue and compression of the vessels by voluntary muscle, combined with valves in the vessels, produces flow.
169
What is the function of the lymphatic system?
System of relatively thin walled vessels that drain excess tissue fluid (lymph) into the blood stream. Transports lymph to lymph nodes for immunological surveillance.
170
What is the tunica intima made up of?
Squamous epithelial cells -termed endothelial. Supported by a basal lamina and a thin layer of connective tissue
171
What is the tunica media made up of
smooth muscle
172
What is the tunical adventitioa made up of?
Connective tissue
173
Why are large arteries eg the aorta termed elastic arteries?
They contain sheets of elastic fibres in their tunica media
174
What is the vaso vasorum?
In large arteries only the inner half of the wall can obtain nutrients from the lumen - therefore thy have their own blood supply- the vaso vasorum
175
What are the three types of capillaries?
Continuous eg muscle, berve, lung, skin. Fenestrated (small pores) eg gut mucosa, endocrine glands, kidney. Sinsuoidal- have large gaps eg liver, spleen, bone marrow
176
What is a pericyte?
Connective tiisue cells that have contractile propetries- often present in capillaries and venules
177
When does a capillary become a venule?
When the vessel begins to acquire intermittent smooth muscle cells in the tunica media
178
What is the difference between veins and arteries?
Thin tunica media/
179
What is a special feature if large veins such as the vena cava?
thick tunica adventitia
180
What are valves?
Extensions of the tunica intima that prevent backward flow in small and medium veins
181
Where is most of the blood in the body?
Peripheral veins
182
Name the agranulocytes?
Lymphocytes, monoctyes
183
What is blood plasma made up of?
Water (90%), proteins (albumin, Ig, clotting factors), nutrients and salts.
184
How can blood be separated?
By spinning in a centrifuge. RBCs most dense, the WBCx the plasma
185
What is serum
Blood without clotting factors
186
How big are RBCs?
7 micrometres
187
What are red blood cells made up of?
Haemoglobin (one third) and a cytoskeletal elements that allow them to deform and slip through small spaces- no nucleus!
188
How long to erithrocytes last in the circulation?
four months
189
How are aged red blood cells removed from the body?
Spleen and liver
190
WHat is a stack of red blood cells called?
Rouleau (rouleaux) - may indicated disease
191
What shape are red blood cells?
biconcave
192
Why do neutrophils strain poorly?
Many granules-dont take up dye
193
What is an important histological feature of neutrophils?
Prominent, multi-lobed nucleus
194
Which cye should be used to stain eosinophils?
Eosin- the granules in eosinphils have an affinity for acidic dyes
195
Where do most eosinophils live?
spleen, lymph nodes and GI tract
196
Describe the nucleus of an eosinphil?
Bilobed nucleus
197
What is contained within the granules of eosinophils?
Hydrolytic enzymes
198
Which is the least common granulocyte?
BAsophils
199
What should be used to stain basophils?
Methylene blue- granules have affinity for basic dyes
200
Describe the nucelus of a basophil?
Bilobed nucleus
201
What is contained in the granules of basophils?
Histamine, heparin and other inflammatory mediators
202
How do basophils cause allergic reactions?
High affinity IgE receptors in their cell membrane are directed against a particular allergen and when they bind their antigen the cell is stimulated to release its granules (termed degranulation
203
Where are macrophages commonly found?
connective tissue- loose
204
Describe the histological features of monocytes?
Numerous small lysosomal granules in theyr cytoplasm. Non-lobulated nucleus (kidney shaped) Largest cells in blood.
205
Give examples of resident cells in the mononuclear phagocytic system
Kupffer cells in liver, microglia in the brain and langerhan's cells in the skin
206
What are the histological features of lymphocytes?
Round nucleus.Thin rim of cytoplasm. No visable granules.
207
What are platelets?
Small (2 micrometres) cell fragments that play a key role in haemostasis (prevent loss of blood)
208
What are the histological features of platelets?
Developed cytoskeleton. Some organelles, no nucleus. Conspicous granules that include coagulation factors.
209
What role do platelets play in haemostasis?
In the process of hemostasis platelets adhere to the site of damage, aggregate and degranulate. They also activate the production of fibrin which participates in clot formation.
210
What is haemopoiesis?
formation of blood cellular components
211
Where is the earliest site for erythrocyte formation?
Outside the embryo in the yolk sac
212
When does haemopoiesis begin?
three weeks gestation
213
Where is the main site of blood formation in the second trimester?
liver (and spleen to some extent)
214
Where is the main site of blood formation after birth?
Bone marrow (in all bones)
215
What bones maitain haemopoiesis once fully matured?
vertebrae, ribs, skull, pelvis and proximal femurs. Marrow in other bone is mainly adipose
216
How are red blood cells produced?
In bone marrow from stem cells. Mature through a series of steps that include haemoglobin production and extrusion of the nucleus
217
What is a reticulocyte?
Newly formed RBC which has granules of RNA in the cytoplasem
218
When is a mature red blood cell formed.
new RBCs circulate the blood for 1-2 days before their RNA is lost and they are now mature.
219
What are megakaryocytes?
Giant cells found in bone marrow. Priduce platelets before undergoing apoptosis.
220
How are platelets formed in megakaryocytes?
As extensions at the outer margin of the cell which fragment from the cell
